2-28. In addition to task-organizing, commanders establish priorities of support during planning and shift priorities during execution as the situation requires. A priority of support is a priority set by the commander to ensure a subordinate unit has support in accordance with its relative importance to accomplish the mission. Priorities of movement, fires, sustainment, and protection all illustrate priorities of support that commanders use to weight the decisive operation or the main effort if the operation is phased. The main effort is a designated subordinate unit whose mission at a given point in time is most critical to overall mission success (ADP 3-0). The main effort is weighted with the preponderance of combat power—the total means of destructive, constructive, and information capabilities that a military unit or formation can apply at a given time (ADP 3-0). Designating a main effort temporarily gives that unit priority of support. Commanders shift resources and priorities to the main effort as circumstances require. Commanders may shift the main effort several times during an operation. When executed, the unit conducting the decisive operation—the operation that directly accomplishes the mission—is always the main effort.